automatic transmission flush

With my past vehicles I'd do the "recommended" flush at 50K to keep the warranty gods happy. After that it's just drain/fill. The longer it's been since a service and/or the older the vehicle the less likely I am to do a flush. I've personally had two trannies die shortly after flushing. One was a previously wrecked truck that was run dry and driven for an unknown period and the flush put it over the edge. The other was a truck with no previous problems. "Power Flushed" it at 90K and within a day it began slipping and clunking. I took it back to the dealer that did the service twice and ended up just trading it in (and I'm sure they disclosed the problem to the new buyer :))

My bottom line is unless it's to satisfy a warranty I'd NEVER "power-flush" a tranny. Drain/fills and filter changes are the best maintenance IMO.